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Ruling Networks with RDL: A Domain-Specific Language to Task Wireless Sensor Networks

Explore Kirsten Terfloth's innovative RDL language, tailored for wireless sensor networks, combining event-centric processing with rule-based programming for fast prototyping and abstraction.

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Ruling Networks with RDL: A Domain-Specific Language to Task Wireless Sensor Networks

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  1. Ruling Networks with RDL:A Domain-Specific Language to Task Wireless Sensor Networks Kirsten Terfloth Institute of Mathematics and Computer Science Freie Universität Berlin, Germany RuleML October 31th, 2008 - Orlando, Florida

  2. MOTIVATION: RULES FOR WIRELESS SENSOR NETWORKS • Abstraction needed for programming wireless sensor networks! • Combination of complex properties to handle – embedded devices, wireless networking, event-centric processing and distribution • Domain-Experts (Biologists, Media Designers, ..) instead of Computer Scientists • Fast Prototyping instead of embedded C • Rule-based programming: • Event-Condition-Action naturally fits the domain • Push model (interrupts: radio, sensors, timers) • Reactive behavior • Language tailored to domain AND operational model to the rescue! KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 2

  3. GENERAL CONCEPT – FACTS • Language is essential part of a middleware framework • Virtual machine running on the nodes to interpret rules • Memory access completely managed • System rulesets can be linked on demand to provide common WSN features KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 3

  4. DATA ABSTRACTION: EVERYTHING IS A FACT! • All data visible to a programmer is wrapped in facts • Named <key, value> tuples • Timestamped for temporal ordering threshold [temp = 25] energy [level = „low“] role [current = „router“] humidity [value = 77] role [current = „sink“] aggregateAccEvents threshold [acc = 100] request [data = „log_data“, timespan = 20, enabled = true] KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 4

  5. EVENT / CONDITION PART OF RULES • Conditions: reason about state AND events • Syntax: Production rule „WHEN“ • Semantics: Event-Condition-Action BUT events are not transient • Reactive rules that operate on event and state • Conditions can feature • Test for existance of specific facts • Evaluation of values of fact properties (simple and range queries) • Unary expressions over both fact properties and sets of facts • Evaluation of conditions is triggered upon insert/update on fact repository • Deletion of facts is not an event KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 5

  6. CONDITION EXAMPLES I: EXISTANCE • IF „newSampleRequest“ rule bootstrap 20 <- exists {newSampleRequest} KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 6

  7. CONDITION EXAMPLE II: RANGE QUERY AND CONSTRAINT CHECK • IF „newSampleRequest“ AND value of property sensor == „humidity“AND value of property reqNum > 12 AND <= 100 rule bootstrapHumidity 40 <- exists {newSampleRequest <- eval ({this sensor} == „humidity“) <- eval ({this reqNum} > 12) <- eval ({this reqNum} <= 100)} KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 7

  8. CONDITION EXAMPLE III: CONJUNCTION • IF „newSampleRequest“ AND nodeID == 3 rule bootstrapIfCorrectNode 11 <- exists {newSampleReqest} <- eval ({system owner} == 3) KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 8

  9. CONDITION EXAMPLE VI: UNARY / BINARY EXPRESSION • IF „newSampleRequest“ AND number of humidity facts in repository > 3 AND increment of the reqNum property of „newSampleReq“ == 5 rule bootstrapAggreagate 11 <- exists {newSampleRequest} <- eval ((count {humidity}) > 3) <- eval (({newSampleRequest reqNum} + 1) == 5) KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 9

  10. ACTION PART OF A RULES • Statements feature • Basic fact manipulation • Define / set / retract • Domain-specific part of the language • Share facts with remote nodes • Sample sensors • Invoke hardware functionality • Execution • Atomic: When a rule triggers, all statements are executed in order • Events arising are buffered to avoid race conditions KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 10

  11. SEMI-CONCLUSION • Execution semantics • Evaluation of rules complies to a priority ordering • No binding of facts to variables: Pattern matching • Language constructs so far allow for • Definition of global rulebase (node-local) ruleset forwarding fact rt_entry [next = 4, sink = 15, cost = 3] rule forwarding 100 <- exists {data_sample} <- exists {rt_entry} -> send {rt_entry next} 100 {data_sample} KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 11

  12. HOW TO ADD MODULARITY TO ENABLE RE-USE? • Rulebase size is very limited (e.g. 17 KB of ROM on MSB ) • Building a cohesive rulebase for all possible rules envisioned is not an option • Language features no binding options for variables • All forward chaining is done by pattern matching on names and values • How to provide a generic interface to match a diversity of facts? KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 12

  13. PATTERN MATCHING AND MODULARITY ruleset forwarding fact rt_entry [next = 4, sink = 15, cost = 3] rule forwarding 100 <- exists {data_sample} <- exists {rt_entry} -> send {rt_entry next} 100 {data_sample} humidity? • Switch of perspective: declarative -> functional • Understand rule to be a function • Polymorphism / function overloading is missing! KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 13

  14. GENERIC MATCHING • Extention of possible types for property values • boolean, integer, String • Add: name • Extension of matching capability to enable referencing to different facts • Benefit: Expression of relational references across rules and ruleset is possible KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 14

  15. RELATIONAL REFERENCING humidity [value = 30] humidity [value = 32] temperature [value = 17] data_sample [sensor = humidity] KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 15

  16. TRANSPARENT FORWARDING ruleset TransparentForwarding public name data_sample = „data_sample“ public name humidity = „humidity“ fact rt_entry [next = 4, sink = 15, cost = 3] rule forwarding 100 <- exists *{data_sample sensor} <- exists {rt_entry} -> send {rt_entry next} 100 *{data_sample sensor} rule sensor_humidity 99 <- exists {humidity} -> define data_sample [sensor = humidity] KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 16

  17. REMARKS • Additional language features • Named filters for frequently requested constraints • Straight-forward integration into modular rulesets • Namespaces and scoping added • Public/private visibility of names and facts KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 17

  18. CONCLUSION • RDL is a domain-specific language explicitly designed for wireless sensor networks • High level of abstraction from hardware percularities • Manual stack management • Event buffering • Interrupt handling • Forward chaining to derive next state • Declarative nature, support for modular rule bases added • FACTS: middleware framework for RDL programs • http://cst.mi.fu-berlin.de/projects/FACTS/index.html • http://cst.mi.fu-berlin.de/projects/FenceMonitoring/ KIRSTEN TERFLOTH RDL: A DOMAIN-SPECIFIC LANGUAGE TO TASK WSNs 18

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